1. Field of the Invention
The present invention relates to a display device and an electronic device using the display device, and more particularly, to the structure of a display device using a transmitted light polarization axis changing device formed of a liquid crystal panel or the like.
2. Description of Related Art
Conventionally, liquid crystal display devices have been used in various recent electronic devices, such as portable telephones, portable music playback devices, timepieces, cameras, VTRs, microwave ovens, and telephones. Display sections of such electronic devices appropriately employ a text information display section for displaying characters, numerals, symbols, and the like by a combination of a plurality of dot regions or segment regions, and an icon display section for displaying icons, for example, predetermined patterns, such as illustrations, special symbols, and marks, by using exclusive one or more segment regions.
The text information display section adopts a dot matrix method in which various character information and the like can be freely rewritten and characters and the like are represented by a group of small dots, and a segment method, such as a seven-segment method for expressing numerals, in which characters and the like are expressed by a combination of a plurality of segments.
In contrast, the icon display section displays illustrations, symbols, words, and the like in a fixed manner, and displays information such as the settings and current situation of the electronic device and a warning to the user in a predetermined fixed form. Specific examples thereof are a display section of a portable device for displaying the remaining quantity of a battery in several stages (an illustration of a battery), a display section of a portable telephone for displaying the strength of radio waves in several stages (an illustration of a radio wave), a display section of an electronic timepiece for showing that the alarm has been set (xe2x80x9cALARMxe2x80x9d), and a display section of a chronograph for showing that timing is stopped (xe2x80x9cSTOPxe2x80x9d).
In a conventional liquid crystal display device using, for example, a known TN or STN liquid crystal display panel, two polarizers are placed on the front and back sides of a liquid crystal cell in an orientation such that the transmitted-light polarization axes thereof are orthogonal to each other, the polarization axis direction of polarized light which has passed through one of the polarizers is changed or maintained according to the presence or absence of an electric field applied to a liquid crystal layer in the liquid crystal cell, and a light blocking state and a light transmitting state of the liquid crystal display panel are switched by causing the polarized light to be blocked by the other polarizer or to be passed therethrough. Since a display surface appears dark in the light blocking state of the liquid crystal display panel and light in the light transmitting state, various information can be displayed by using the dark and light colors.
In order to form an icon display section in the above display device using the liquid crystal display panel, however, transparent electrodes, reflecting electrodes, and the like formed on the inner surface of a panel substrate of the liquid crystal display panel must be formed in the shape of the icons. For this reason, when producing liquid crystal display panels having different icon forms, liquid crystal cells must be designed and produced for each icon. Even if the other portions, for example, text information display sections, remain just the same in structure, the panel structure cannot be commonly used. In this case, in order to form icons having fine patterns and lines and complicated icons using a plurality of colors, an electrode pattern also needs to have a fine structure. This makes production significantly difficult, and is not practical.
In contrast, another method is known in which constantly visible icons are formed on a panel substrate of a liquid crystal display panel by printing or by other methods, and a display for indicating the selection state of the icons is produced by the liquid crystal display panel as required. In this case, however, the icons are constantly displayed, and therefore, visibility is low. Moreover, the indication display is also required, and this occupies a large part of the display area.
In a liquid crystal display device having both a text information display section and an icon display section, since text information and an icon display or an icon indicating display are shown in the same color on the same background, they are completely harmonized. For example, an icon for drawing the user""s attention is inconspicuous, and therefore, is not noticed by the user.
In particular, in the display sections of portable devices, such as portable telephones, portable CD players, and portable MD players, since multiple abstract and small icons are displayed in a small display area, it is difficult to grasp displayed information.
The present invention aims to solve the above problems, and an object of the present invention is to realize a new display technique for a display device for reliably producing icon displays of various designs and allowing displayed information to be easily grasped, and to provide a display device which provides high visibility in an electronic device and the like.
An exemplary embodiment provided by the present invention in order to achieve the above object is a display device including a transmitted light polarization axis changing device for changing the polarization axis of transmitted light in each control region, first and second polarization separating elements placed on both sides of the transmitted light polarization axis changing device, an optical modulation layer formed or placed in a predetermined modulation pattern on the side of the second polarization separating element opposite from the transmitted light polarization axis changing device, and a light reflecting layer placed on the side of the optical modulation layer opposite from the second polarization separating element, wherein the first polarization separating element emits a linearly polarized light component, polarized in a first direction, of light entering from the side opposite from the transmitted light polarization axis changing device toward the transmitted light polarization axis changing device, and emits a linearly polarized light component, in the first direction, of light entering from the transmitted light polarization axis changing device toward the opposite side, the second polarization separating element transmits a linearly polarized light component, in a second direction, of light received from the side of the transmitted light polarization axis changing element toward the optical modulation layer, reflects a linearly polarized light component, in a third direction different from the second direction, of the light received from the side of the transmitted light polarization axis changing device toward the transmitted light polarization axis changing device, and emits a linearly polarized light component, in the second direction, of light received from the optical modulation layer toward the transmitted light polarization axis changing device, a display pattern portion is formed at a position in the modulation pattern of the optical modulation layer corresponding to the control region in a plane, and the control region completely covers a region of the display pattern portion necessary as a display portion.
According to this embodiment, when external light enters the first polarization separating elements, a linearly polarized light component thereof in the first direction is transmitted therethrough and enters the transmitted light polarization axis changing device. The linearly polarized light component is caused to appropriately change the polarization axis by the transmitted light polarization axis changing device, and then enters the second polarization separating element. The second polarization separating element transmits a linearly polarized light component in the second direction of incident light, and reflects a linearly polarized light component in a third direction. Therefore, when the linearly polarized light component in the first direction is turned into a linearly polarized light component in the second direction by the transmitted light polarization axis changing device, the light passes through the second ploarization. When the linearly polarized light component in the first direction is turned into a linearly polarized light component in the third direction by the transmitted light polarization axis changing device, the light is reflected by the second polarization separating element. The light reflected by the second polarization separating element passes again through the transmitted light polarization axis changing device and the first polarization separating layer, and is emitted outside. In contrast, the light passed through the second polarization separating element is modulated by the optical modulation layer, is reflected by the light reflecting layer, passes again through the second polarization separating element, the transmitted light polarization axis changing device, and the first polarization separating element, and is emitted outside.
Accordingly, external light is reflected and emitted outside by the second polarization separating element, or modulated by the optical modulation layer and is reflected and emitted outside by the light reflecting layer, according to the control state of the control region of the transmitted light polarization axis changing device. Therefore, it is possible to switch the display in each control region depending on which optical path is selected. Since the region necessary for a display portion of the display pattern portion formed inside the modulation pattern of the optical modulation layer is completely covered by the control region, even when the pattern, shape, color, and the like of the display pattern portion are fine or complicated, the shape of the control region itself need not be fine or complicated. This eliminates the necessity to complicate the structure for forming the control region. As a result, the display pattern portion can be formed in an arbitrary pattern, color, or shape, and it is possible to easily form display contents that are easy to recognize and detect. Furthermore, the display pattern portion can be easily changed so as to provide a different display structure by replacing only the optical modulation layer without changing the control region.
In the above configuration, it is preferable that the transmitted light polarization axis changing device control the state of the control region so as to turn the linearly polarized light in the first direction into one of linearly polarized light in the second direction and linearly polarized light in the third direction. It is satisfactory as long as the light reflecting layer in the above configuration has a function of reflecting at least a part of incident light so as to contribute to display, and the light reflecting layer need not have a high reflectance for all the light. While it is most preferable that the second direction and the third direction be orthogonal to each other, the present invention is not limited thereto.
According to an exemplary embodiment it is preferable that the peripheral edge of the control region extend outside the peripheral edge of the display pattern portion in a plane in a direction to widen the region. According to this embodiment, since the peripheral edge of the control region extends outside the display pattern portion in a plane, extra space is formed by the extending portion. For this reason, even when pattern displacement in a planar direction is caused, between the transmitted light polarization axis changing device and the optical modulation layer, the display form of the necessary display portion of the display pattern portion is less prone to be influenced thereby, and the risk of display failure is reduced. As long as the shape of the display pattern portion is changed within a predetermined range, display remains unchanged because of the extra space obtained by the extending portion, and therefore, the modulation pattern of the optical modulation layer can be changed without changing the pattern shape of the control region.
According to another exemplary embodiment, it is preferable that a portion of the peripheral edge of the control region close to another control region be retreated in a plane from the peripheral edge of the display pattern portion in a direction to narrow the region, and that other portions of the peripheral edge of the control region other than the close portion extend in a plane outside the peripheral edge of the display pattern portion in a direction to widen the region. According to this embodiment, even when a plurality of control regions are close to one another, the distances therebetween become larger than the distance between corresponding display pattern portions at the close portions, and the control regions extend outside the display pattern portions at the portions other than the close portions. Therefore, it is possible to prevent control failure due to short-circuiting and mutual interference resulting from the close relationship between the control regions. Even when pattern displacement in a planar direction is caused between the transmitted light polarization axis changing device and the optical modulation layer, the display form of the necessary display portion of the display pattern portion is less prone to be influenced thereby, and the risk of display failure is reduced. As long as the shape of the display pattern portion is changed within a predetermined range, display remains unchanged because of the extra space obtained by the extending portion, and therefore, the modulation pattern of the optical modulation layer can be changed without changing the pattern shape of the control region.
According to another exemplary embodiment, it is preferable that a display form produced by emission of the linearly polarized light component in the third direction reflected by the second polarization separating element and a display form produced by emission of a linearly polarized light component in the second direction, which is not modulated by the optical modulation layer, but is reflected by the light reflecting layer, be substantially the same. According to this embodiment, even when the control region is formed to be larger than a display portion of a corresponding display pattern portion, a display form obtained by light reflected by the light reflecting layer in the control region on the periphery of the display portion of the display pattern portion and a display form obtained by light reflected by the second polarization separating element outside the control region are substantially the same, thereby improving display quality on the periphery of the display portion.
According to another exemplary embodiment, it is preferable that the light reflecting layer be formed of a third polarization separation element having the same structure as that of the second polarization separating element so as to reflect a linearly polarized light component in the second direction of light received from the side of the second polarization separating element toward the second polarization separating element. According to this embodiment, light is reflected and emitted outside by the second polarization separating element or the third polarization separating means according to the state of the control region. Since the second polarization separating element and the third polarization separating element have the same structure, the reflection form is substantially similar in both cases in which the linearly polarized light component in the third direction is reflected by the second polarization separating element and in which the linearly polarized light component in the second direction is reflected by the third polarization separating element. As a result, a display form obtained by light reflected by the second polarization separating element and a display form obtained by light reflected by the third polarization separating element are similar to each other.
In this case, it is preferable that the third polarization separating element be just the same as the second polarization separating element. When the second direction and the third direction are orthogonal to each other, it is preferable that the third polarization separating element be placed so that it is rotated by 90xc2x0 on the optical axis relative to the second polarization separating element.
According to another exemplary embodiment, it is preferable that a light source be placed on the side of the light reflecting layer opposite from the optical modulation layer and that the light reflecting layer transmit at least a part of light received from the light source. According to this embodiment, since at least a part of light received from the light source is transmitted through the light reflecting layer, the transmitted light sequentially passes through the optical modulation layer, the second polarization separating element, and the transmitted light polarization axis changing device. In this case, according to the state of the control region of the transmitted light polarization axis changing device, when the linearly polarized light component in the second direction passed through the second polarization separating element is turned into a linearly polarized light component in the first direction in the control region, it is emitted outside via the first polarization separating element. When the linearly polarized light component in the second direction is turned into a linearly polarized light component in a direction substantially orthogonal to the first direction by the control region of the transmitted light polarization axis changing device, it is blocked by the first polarization separating element and is not emitted outside. Therefore, it is possible to partially display the display modulated by the optical modulation layer based on light from the light source even in a dark environment.
In this case, when the third polarization separating element is provided, it is preferable that the third polarization separating element reflect a linearly polarized light component in the second direction from the second polarization separating element and transmit a linearly polarized light component in the second direction from the light source. Therefore, for example, it is preferable to place the third polarization separating element so as to be rotated on the optical axis by a predetermined angle of less than 90xc2x0 from a position for reflecting a linearly polarized light component in the second direction. The third polarization separating element may be automatically or manually rotated when display is viewed by external light and when display is viewed by light from the light source. In this case, the rotation angle is, for example, 90xc2x0.
According to another exemplary embodiment, it is preferable that a plurality of display pattern portions produce an integrated icon display by combining display portions thereof.
According to this embodiment, since an integrated icon display is produced in various forms by combining display portions of a plurality of display pattern portions, it is possible to selectively display a plurality of kinds of icons in the same region, to change the icon display form, and to activate the icon display.
There is provided a display device including a transmitted light polarization axis changing device for changing the polarization axis of transmitted light in each control region, first and second polarization separating element placed on both sides of the transmitted light polarization axis changing device, an optical modulation layer formed or placed in a predetermined modulation pattern on the side of the second polarization separating element opposite from the transmitted light polarization axis changing device, and a light reflecting layer placed on the side of the optical modulation layer opposite from the second polarization separating element, wherein the first polarization separating element emits a linearly polarized light component, polarized in a first direction, of light entering from the side opposite from the transmitted light polarization axis changing device toward the transmitted light polarization axis changing device, and emits a linearly polarization component, in the first direction, of light entering from the transmitted light polarization axis changing device toward the side opposite from the transmitted light polarization axis changing device, wherein the second polarization separating element transmits a linearly polarized light component, in a second direction, of the light received from the side of the transmitted light polarization axis changing device toward the optical modulation layer, reflects a linearly polarized light component, in a third direction different from the second direction, of the light received from the side of the transmitted light polarization axis changing device toward the transmitted light polarization axis changing device, and emits a linearly polarized light component, in the second direction, of light received from the side of the optical modulation layer toward the transmitted light polarization axis changing device, and wherein a display pattern portion is formed at a position in the modulation pattern of the optical modulation layer corresponding to the control region in a plane, and an integrated icon display is produced by a combination of a plurality of display pattern portions. According to this embodiment, it is possible to selectively display a plurality of kinds of icons in the same region, to change the icon display form, and to activate the icon display.
There is provided an electronic device having a display device of the above exemplary embodiments. The electronic device includes electronic timepieces, various domestic electrical appliances having an electronic control section, and portable electronic devices, such as portable telephones and portable information terminals. In particular, the application to electronic devices with a limited display area, for example, portable electronic devices, such as portable telephones and electronic wristwatches, makes it possible to relatively easily form a control region and to obtain a superior icon display.
According to various exemplary embodiments, it is preferable that the display portion of the display pattern portion be structured to show an icon display.
According to the above exemplary embodiments, a liquid crystal panel may be used as the transmitted light polarization axis changing device. The second polarization separating element and the third polarization separating element may have a multilayered structure formed by stacking a first layer and a second layer having different refractive indices in a predetermined direction in a plane and equal refractive indices in a direction other than the predetermined direction. In this case, it is preferable that the predetermined direction and the other direction be orthogonal to with each other. Furthermore, it is preferable that the first layer and the second layer be repeatedly and alternately stacked while gradually changing the thicknesses thereof so as to operate within a predetermined wavelength range.